In heat exchangers that have a high aspect ratio (the ratio of width to height), it is frequently necessary to locate the tube runs in a generally horizontal plane to minimize cost. Typical of such heat exchangers are evaporators and condensers as may be found in the air conditioning systems of off-highway vehicles, air conditioning systems for recreational vehicles, and in truck refrigeration systems. Particularly when used as evaporators, conventional serpentine louvered fins coupled with horizontal tube placement provides problems with water drainage due to the hold up of water between the fins. That is to say, it is necessary in evaporator applications that provision be made to drain moisture condensing on heat exchanger parts to prevent freeze-up which would block air flow and drastically impede efficiency.
As a consequence of these and other considerations, high aspect ratio evaporators and other heat exchangers have historically been produced using round tube plate fin technology. The tubes are oriented horizontally and the plate fins vertically to allow water to drain down the fins, around the tubes and out through the bottom of the heat exchanger. However, when compared to brazed, parallel flow type heat exchangers, performance of round tube plate fin heat exchangers suffers in three main areas.
For one, the round tubes substantially occlude the frontal area of the heat exchanger through which air passes. As a consequence, poor air side heat transfer results.
A second problem is that mechanical bonds between the tubes and the plate fins conventionally employed in such heat exchangers are incapable of reliably providing intimate, good heat exchange contact between the tubes and the fins and as a result, poor fin-tube bonds frequently reduce heat transfer.
A third problem is that the use of round tubes requires relatively large fin heights (fin height being the length of the fin between the center lines of two adjacent tubes). These large effective fin heights result in poor fin efficiency.
Still another problem that has sometime occurred in heat exchangers generally is undesirably low air side area. The lack of sufficient area impedes heat transfer on the air side as a quick review of Fourier's law will readily show. Consequently, it would be desirable to increase air side surface area without increasing fin height to the point where poor fin efficiency results.
The present invention is directed to overcoming one or more of the above problems.